Access to prenatal and intrapartum services for low-income women is a critical problem in many areas of the country (1-4). Ten percent of women delivering in San Diego County receive no prenatal care (39). Women who do not receive prenatal care have been shown to have poorer perinatal outcomes and increased neonatal medical costs (35,40). Retrospective studies of out-of-hospital birth centers have suggested that they are as safe and are less expensive than traditional hospital delivery (19-25). The objective of this study is to evaluate whether the out-of-hospital birth center model is a safe and cost-effective alternative for the delivery of prenatal and perinatal services for underserved, low-income women. The findings of this study could have significant implications for the delivery of perinatal services nationwide. The San Diego Birthplace provides comprehensive prenatal and perinatal services through a collaborative management model of nurse midwives and obstetricians. Low risk pregnant women deliver in an out-of-hospital birth center. Women who are high risk or develop complications during pregnancy deliver in the hospital. The specific aims of this study are to evaluate the maternal and infant outcomes and costs of care at the San Diego Birthplace as compared to a traditional model using physician providers and hospital delivery. The study would be the first prospective cohort study comparing these two health care models in the U.S. Women will be followed from entry into prenatal care through six weeks postpartum; infants through the first year of life. The study population will be primarily low-risk, Medicaid eligible, hispanic women. A four year study with a two year entry period is planned. The total sample size will be approximately 3700 subjects. Steps will be taken to assure comparability of the index and comparison populations based on perinatal risk. Data will be collected primarily through the use of medical and financial record abstraction and self- administered questionnaires completed at selected points during the follow-up period. Both crude and adjusted prenatal, intrapartum, postpartum and infant mortality and morbidity rates from the two models will be compared. Cost-effectiveness and acceptance of the birth center model by a low-income population will also be evaluated.